The invention relates to a method for inhibiting breakthrough of driving fluid via a relatively permeable geological layer of a stratified hydrocarbon-bearing subterranean formation into a production well. More particularly, the invention relates to a method for reducing the permeability of one or more relatively permeable geological layers of a subterranean formation.
When producing hydrocarbons from a subterranean formation, water and/or steam may be injected into an injection well to help drive the production of hydrocarbons. The hydrocarbon is pressed by the water, steam, steam foam or froth and/or other driving fluid through the geological layers into the production well, thereby enhancing the production of hydrocarbon. Stimulation of hydrocarbon production by injection of driving fluids into the formation is a technology used in Improved Oil Recovery (IOR).
The break through of driving fluid from injection wells to production wells is a common problem, in areas such as heavy oil producing areas in Alaska and Canada. The flow path is thought to be a combination of fractures and worm holes. Often a possible flow through matrix is suggested. This breakthrough of driving fluid is a big disadvantage, as the water/oil ratio retrieved from the production well may rapidly increase and become more and more unfavorable during the lifetime of the oil field.
In some cases, produced water is often disposed of by pumping the water into injection wells. In some instances, however, there exist subterranean flow ways from the injection well to the production well, such that the injected water flows to the production well. This can lead to an increase in the amount of water produced, or in some situations (such as heavy oil) may destabilize the producing formation. Often the flow ways are flow-paths along fractures and fissures, although in some cases the flow may be through the formation matrix.
Therefore, it would be be desirable to have methods which shut off or significantly minimize the flow of injected driving fluid to the producing wellbore. Such a need is met, at least in part, by the following invention.